1. Technical Field
The present invention relates generally to surgical instruments and more specifically to surgical compressors and similar instruments.
2. Background Information
In some surgical procedures, a surgeon may need to exert compressive force on objects disposed within the human body. One such surgical procedure is minimally invasive spinal fusion surgery.
Minimally invasive spinal fusion surgery involves accessing the spine via a small incision and rigidly attaching two or more vertebrae with a fixation rod or other element. Typically, the surgeon first inserts an access port into the incision, to both hold open the incision and create a stable work platform. The access port typically has an expandable distal end that holds back tissue, and that rests upon bone to prevent muscle creep and stabilize the port. With an access port in place, the surgeon usually screws or otherwise is affixes bone screws or other constructs to two or more vertebrae. A spinal fixation rod is attached between the bone screws, held in place, for example, by set screws or other fasteners. The spinal fixation rod holds the vertebra in a desired spatial relationship until spinal fusion or other healing occurs.
In many cases, it is desirable for the spinal fixation rod to hold the vertebra in a compressed state. Thus, the surgeon applies compressive force between bone screws and then secures the spinal fixation rod to maintain the compressive force. To apply the compressive force, the surgeon may use a surgical compressor. Most existing surgical compressors may be classified into two general types: cable-type compressors and lever-type compressors.
Cable-type compressors typically employ a cable that wraps around bone screws. The surgeon applies tension to the cable by manipulating a ratcheting mechanism, such as a ratcheting pistol grip. The ratcheting mechanism exerts and holds tension upon the cable. The greater the tension, the greater the compression between the bone screws. While many cable-type compressors advantageously permit single-handed operation, they suffer many shortcomings. For example, it may be difficult to properly arrange the cable about the bone screws in a confined surgical space. Further, a cable-type compressor may provide unwanted mechanical advantage, rendering it difficult for the surgeon to judge the actual compression being exerted.
Lever-type compressors typically employ two lever arms arranged to resemble a pliers. The surgeon places the distal ends of the lever arms about the bone screws. By gripping and squeezing together the proximate ends of the arms, the surgeon may apply compression. To maintain the compression, such that the surgeon need not continually squeeze the lever arms together, some lever-type compressors have a spring-loaded is ratchet bar that may be used to couple the arms. The surgeon may cause the ratchet bar to lock the two lever arms in a fixed relative position to maintain compression.
One shortcoming of conventional lever-type compressors with ratchet bars is that they require two hands to operate: one hand to squeeze together the lever arms, and another hand to move the ratchet bar into place, or out of place. The need for two hands prevents the surgeon from simultaneously manipulating some other surgical instrument or performing some other task. This is especially limiting in complicated surgeries.
Accordingly there is a need for an improved surgical instrument that overcomes the shortcomings of prior designs.